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T O P I C R E V I E W

LM-12

In the Apollo 7 through Apollo 10 crew walkout photos, the EMU neck rings are blue. In the Apollo 11 through Apollo 17 crew walkout photos, the EMU neck rings are red. Why the change?

In the official Apollo 11 crew portrait, only Aldrin is wearing a red EMU neck ring.

A two-colour system could have distinguished a flight suit from a training suit, or an A7L suit from an A7LB suit, or a CMP suit from a CDR/LMP suit, but none of those seem to apply.

Just an observation.

MattJL

Odds are that I'm wrong, but maybe it has something to do with the intended usage of the suit. If I recall correctly, save for 9, when Schweickart went on EVA, none of the flights up until 11 had the outer helmet with the gold visor. Possibly there's a latch between the outer helmet and the neck ring that wasn't present on the blue neck ring?

Now, what I'm curious about is where Armstrong's and Collins' blue neck ringed suits are today, if they still exist.

You may have noticed that in the Apollo crew portraits, the left wrist locking ring is blue and the right wrist locking ring is red. The Gemini suits were like that too.

MattJL

Looking back at 11's portrat, it seems like Aldrin's red neck ring is a cover of some sort over the blue one (There's blue inside of the neck ring and a blue attachment point is visible as well). And yet it can't be, because the locking mechanism is red as well. Hmm.

Perhaps it was intended to differentiate between the commander's and the LMP's helmets, as they weren't labelled as clearly as, say, the gloves.

DG27

The neck ring of the Apollo A7L suit was originally anodized blue in color. During use of the A7L suit, a design change was made to the vent port between the suit neck ring and the helmet. This change enlarged the vent port and slightly clocked its position on the neck ring. The color of the neck ring was changed from blue to red to make a clear distinction between the two vent port designs.

Thus an early (blue) A7L helmet would not get adequate vent flow on a later (red) neck ring suit and vise versa due to the changes in size and position of the vent port. A helmet with a blue neck ring will actually latch into a red suit neck ring but the vent ports will be misaligned. The first use of A7L suits with red neck rings was on the Apollo 11 mission. All subsequent A7L suits used the red neck rings as well as the A7LB suits.

The Apollo suit-side neck ring is actually made up of multiple parts, and all of them were initially anodized blue. When the vent port design change was made only the outer shell of the suit-side neck ring was changed in color from blue to red. All the other parts of the suit-side neck ring (with the exception of the suit-side vent port which was also changed from blue to red) remained blue. This is why the inside of a red suit-side neck ring is blue.

Further, the red neck rings included engraved wording stating that a red helmet neck ring should only be used with a red suit neck ring. Similar wording was on the red suit neck rings as well.

Crew photos were not necessarily taken with the crew wearing their flight spacesuit. Thus crew photos usually show a mix of neck ring colors as they used the suits that were available at the time of the photo.In addition, crew training used whatever suits were available at the time. Only flight-day walk-out or in-flight photos will show what was actually used on the mission.

One additional note: In the Apollo 11 crew photo, only Collins is holding a helmet, both Armstrong and Aldrin are holding the LEVA without the helmets inside. The “red” color visible inside Armstrong’s LEVA is the interior of the LEVA shell which is red colored plastic.

Hope this helps.

LM-12

Yes, that helps a lot. Thanks for the detailed explanation.

MattJL

Out of curiosity, what led to the change in size and position of the vent? Seems to be a bit sudden in my opinion.

DG27

Good question. Unfortunately, I have not found any documentation which describes why the change was made.

A possible explanation for modifying the vent port would be to fix a problem with visor fogging or inadequate CO2 washout in the helmet. So I checked the Mission Reports for Apollo 7 through 11 but there was no mention of any concerns with the helmet vent flow or any changes identified in the EMU from one mission to the next. The only EVA activity prior to Apollo 11 was the in-flight EVA on Apollo 9. The Apollo 9 Mission Report specifically states that no visor fogging occurred during the in-flight EVA.

So without specific documented evidence, I can only surmise that there may have been some problem during other suit use, such as lunar surface EVA training or metabolic load tests, which indicated a marginal vent flow to the helmet for EVA activity.

During IVA suit use the inlet gas to the suit is split equally between flow to the helmet and flow to distribution ducts in the waist area of the suit. When the suit is used for EVA, the diverter valve next to the blue inlet gas connector is set to the EV position. This diverts all inlet gas directly to the helmet, from where it then flows into the rest of the suit. So for EVA activity where the metabolic loads are the highest, the suit designers wanted to maximize vent flow to the helmet. One can make the argument that since Apollo 11 is the first mission where the lunar surface EVA activity occurs (ie high metabolic activity), that mission is where the enlarged vent port really needed to be in use. However this is speculation on my part.

I need to make a correction to my earlier post regarding the specific changes in the vent port. The vent port was enlarged, but mounted in the same location. Thus there was no change in clocking of the vent port. I pulled some hardware out and realized what I thought was a shift in position of the vent port was really slack between the mounting tang on the vent fitting and the mating alignment slot on the neck ring. When properly aligned via the mounting screws holes, the centerline of the vent port is the same between the blue and red neck rings. But the size of the vent port opening is significantly different between the two.

In doing some literature research, I was successful in locating a reference to an Engineering Change Proposal (ECP) submitted on August 28 1968 to “Redesign A7L Helmet Side and Suit Side Neck Ring”. Unfortunately there is no description of the ECP content, only the title and date. Without the specific wording of the ECP, I can only guess that this may have been the decision point where the vent port (and resulting neck ring color change) was submitted for implementation. A date of August 68 would give sufficient time to implement the design change for the first suits actually needing improved vent flow for lunar surface EVA activity, which would be Apollo 11.

Hope this helps.

LM-12

Great resesarch. If there was some type of EVA-related vent flow problem in the pressure helmet, that certainly would explain the need for a neck ring redesign.